1. Field of the Invention
The present invention relates to displays for pilots of aircraft and in particular to a programmable symbology for defining a geometric form in the visual field of the pilot providing a virtual representation of a geometric shape surrounding the aircraft providing information to the pilot about the position and orientation of the aircraft and its surroundings.
2. Description of the Prior Art
Aircraft, including helicopters, are highly complex systems comprised of a large number of complex, integrated subsystems that requires frequent monitoring for safe aircraft operation. Each of these subsystems generates a significant amount of status data. Additional flight complications such as nap-of-the-earth (NOE), adverse weather, and/or night flying add to the importance of aircraft status data, and also increases the amount of monitoring required. These types of flight operations require the pilot to maintain a continual spatial awareness of aircraft orientation and/or location with respect to the external world in addition to continual monitoring of the status of aircraft subsystems.
The task of monitoring the status of the various aircraft subsystems may conflict with the tasks of maintaining continual spatial and situational awareness of the external world. To monitor the status of aircraft subsystems, the pilot may have to divert his attention from the observation of the external world outside the cockpit to reference generated status data. Such diversions may lead to losses, in varying degrees, of spatial and/or situational awareness of the external world, which, in turn, may lead to less than optimal flight control, especially during high pilot workload flight operations.
U.S. Pat. No. 5,296,854, issued Mar. 22, 1994 to Hamilton, et al., illustrates a virtual image display system providing video displays based upon virtual images of the external world having synchronized structural outlines superimposed on the video displays to a pilot operating an aircraft such as a helicopter in non-visual flight conditions. The virtual image display system includes a virtual imaging subsystem for generating virtual images of the external world, a video display subsystem for generating video images based upon the virtual images and for displaying the video images for the pilot's viewing, a sensing means for providing signals corresponding to the spatial location and perspective of the video display subsystem, a map comprising structural outlines corresponding to structural members forming the canopy structure of the helicopter, and a computer subsystem providing electronic interfacing between the elements of the virtual image display system, for synchronizing the orientation of the virtual imaging subsystem with the video display subsystem, and for processing the virtual image signals to provide signals to the video display subsystem to generate video displays. The computer utilizes the helmet position signals to define the relative position and orientation of the video display subsystem in the cockpit, and utilizes such definition to reconstruct structural outlines from the map that are synchronized to the perspective of the video images. The synchronized structural images are superimposed upon the video display.
U.S. Pat. No. 5,072,218, issued Dec. 10, 1991 to Spero et al., shows images provided to a pilot in an aircraft over-flying the earth by means of a helmet mounted display system. The position and attitude of the aircraft with respect to the earth and the attitude of the helmet with respect to the aircraft are monitored in order to convert a plurality of stored earth position signals into helmet coordinates. Earth points which are viewable by the pilot are displayed using symbolic images thereof such that the symbolic images coincide, from the pilot's point of view, with the actual positions of the viewable points on the earth.
U.S. Pat. No. 4,740,779, issued Apr. 26, 1988 to Cleary, et al., describes a panoramic display system for an aircraft comprising a display screen and line generation means for generating a line image on the display screen. The position of the line image on the display screen corresponds to the position of a projection of an artifact external to the aircraft onto an imaginary window to an eye point within the aircraft. The eye point is positioned on the opposite side of the window from the artifact. The line image may be generated by determining the position of a great circle on a sphere having its center at the eye point, such that the position of the great circle corresponds to the artifact projected onto the sphere to the eye point. The position of the line image on the display screen corresponds to the position of the great circle on the sphere. The display system may comprise a plurality of display screens positioned adjacent to one another such that each can be viewed from a single viewing point. Partial line images are generated on each display screen such that the position of each partial line image corresponds to the position of the projection of the artifact onto a window portion to the eye point. The eye point is common to all window portions, and the spatial relationship of the window portions with respect to one another is congruent with the spatial relationship of the display screens with respect to one another.
U.S. Pat. No. 4,763,280, issued Aug. 9, 1988 to Robinson, et al., claims a system for the production of real-time, computer-generated images as for projection on a curvilinear surface as on the inside of a dome. A general-purpose computer provides data for visual images and supplies the data in an ordered format. Such data is processed first with regard to viewpoint and second with regard to channel operation. Specifically, viewpoint processing incorporates an object manager and a polygon manager. Channel processing includes a geometric processor and a display processor. The display processor drives a projector for illuminating a spherical surface with the desired images. The geometric processor incorporates several well known elements including a rotator, clippers, a slope calculator and polygon buffer. Additionally, the geometric processor incorporates a segmenter and mapper which replaces the traditional perspective divider to process the data so as to generate images for curvilinear projection. The segmenter tests the character of polygon edges in spherical coordinate format and corrections are performed on data in the same format. Segmentation is performed on data in a rectangular coordinate format.
U.S. Pat. No. 4,305,057, issued Dec. 8, 1981 to David R. Rolston, shows a Heads-Up Display system which displays an attitude reference to pilots in order to provide a reference display system as a primary flight instrument. The Heads-up Display system uses a pitch ladder system based on Euler angle data which eliminates the erratic motion or “flip-flop” of the typical pitch ladder which is inherent and unavoidable when pitching near plus or minus 90. degree., by utilizing a flexible graphics display which presents the pilot with a heads-up view as if he were located inside and at the center of an imaginary sphere which has heading and pitch angle information marked on its inner surface. The display of appropriately curved bars as opposed to a straight bar pitch ladder for attitude reference more realistically depicts to the pilot the aircraft situation relative to the outside world. This presentation is more easily and more reliably interpreted by the pilot and simplifies the recognition and recovery from unusual attitudes. In addition, ground track, yaw rate, turn rate information is available over the entire HUD field-of-view, thus there is no need for the pilot to redirect his attention away from his primary point of interest, the velocity vector, to obtain heading and track information. Appropriate equations are evaluated to obtain line-of-sight angles from the aircraft longitudinal axis to the desired pitch and heading points on the pitch ladder display. Such equations are solved by computer techniques for a sufficient number of intersecting points to complete the display and the graphics hardware connects the points to form the segments of the pitch ladder which represent the imaginary lines on the sphere and displays the same in the pilot's field-of-view.
What is needed is symbology in the visual field of the pilot representing the position of the aircraft in space relative to the ground or external surfaces enabling the pilot to visually determine the orientation and position of the aircraft, especially relative to landing.